RESUMO
The relationship between translation and mRNA turnover is critical to the regulation of gene expression. One major pathway for mRNA turnover occurs by deadenylation, which leads to decapping and subsequent 5'-to-3' degradation of the body of the mRNA. Prior to mRNA decapping, a transcript exits translation and enters P bodies to become a potential decapping substrate. To understand the transition from translation to decapping, it is important to identify the factors involved in this process. In this work, we identify Sbp1p (formerly known as Ssb1p), an abundant RNA binding protein, as a high-copy-number suppressor of a conditional allele in the decapping enzyme. Sbp1p overexpression restores normal decay rates in decapping-defective strains and increases P-body size and number. In addition, Sbp1p promotes translational repression of mRNA during glucose deprivation. Moreover, P-body formation is reduced in strains lacking Sbp1p. Sbp1p acts in conjunction with Dhh1p, as it is required for translational repression and P-body formation in pat1Delta strains under these conditions. These results identify Sbp1p as a new protein that functions in the transition of mRNAs from translation to an mRNP complex destined for decapping.
Assuntos
Endorribonucleases/genética , Regulação Fúngica da Expressão Gênica , Proteínas de Choque Térmico HSP70/metabolismo , Biossíntese de Proteínas/genética , Estabilidade de RNA , Proteínas de Ligação a RNA/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/genética , Alelos , RNA Helicases DEAD-box , Proteínas de Ligação a DNA/genética , Endorribonucleases/metabolismo , Repressão Enzimática , Deleção de Genes , Glucose/metabolismo , Proteínas de Choque Térmico HSP70/análise , Proteínas de Choque Térmico HSP70/genética , Proteínas de Ligação ao Cap de RNA , RNA Helicases/genética , RNA Fúngico/metabolismo , RNA Mensageiro/metabolismo , Proteínas de Ligação a RNA/análise , Proteínas de Ligação a RNA/genética , Ribonucleoproteínas/metabolismo , Saccharomyces cerevisiae/química , Saccharomyces cerevisiae/enzimologia , Proteínas de Saccharomyces cerevisiae/análise , Proteínas de Saccharomyces cerevisiae/genética , Supressão GenéticaRESUMO
In C. elegans, tra-2 mRNA nuclear export is controlled by a 3'UTR element, the TRE. In the absence of TRA-1, the TRE retains tra-2 mRNA in the nucleus. The binding of TRA-1 to the 3'UTR overcomes this retention resulting in export of a TRA-1/tra-2 mRNA complex. Here, we find that, unlike most mRNAs, tra-2 mRNA exits the nucleus via an alternative pathway to NXF-1 that requires CRM1 activity. Inhibition of export by NXF-1 depends upon the TRE, CeNXF-2, CeREF-1, and CeREF-2. Removal of the TRE or any one of these factors results in export of tra-2 by NXF-1. NXF-2 and REF-1 specifically bind the TRE, suggesting that they directly control tra-2 mRNA export. Furthermore, choice of proper export pathway affects tra-2 translational control. Therefore, tra-2 mRNA export is highly regulated and plays an important role in development by regulating the activity of tra-2 mRNA in the cytoplasm.
